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Abstract

Cast irons are good examples of materials which are more sensitive to chemical composition and production conditions. In this research to improve casting quality, solidification and nucleation process in grey cast iron was investigate. In particular, attempts have been made to rationalize variation in eutectic cells with nucleation sites and eutectic solidification undercooling. Four castings with different diameter and similar chemical composition and pouring temperature and different inoculant percentage was casted. The cooling curve and maximum and minimum undercooling for each castings was measured. Also optical metallography and image analyzer has been used to determine the average eutectic cells diameter, and linear and surface densities, and volume density was calculated. The results of this research show a competitive behavior between nucleation sites and eutectic undercooling. Higher nucleation sites and higher eutectic undercooling cause higher eutectic cell density. But increasing nucleation sites by introducing inoculants to molten metal, is accompanied with reduction in eutectic undercooling. It means that inoculation and undercooling have opposite effect on each other. So, to achieve maximum cell density, it is necessary to create an optimization between these parameters.
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Abstract

In this research reactive powder concrete (RPC) was prepared using sand from North Sinai. The mechanical properties of locally cast RPC were investigated and evaluated by studying the effects of using different cement and silica fume contents and new steel fi bers’ aspect ratios as reinforce-ment for RPC. Specimens’ preparation, curing regimes and testing procedures to evaluate the com-pressive strength, the modulus of elasticity, the indirect tensile strength and the fl exural strength were discussed. A compressive strength of 154.5 MPa, indirect tensile strength of 11.98 MPa, mod-ulus of elasticity of 45.1 GPa and fl exural strength of 30.26 MPa have been achieved for reinforced RPC contains 800 kg/m³ cement content and silica fume content 30% of cement weight. The test results showed some improvements by increasing cement and silica fume contentsas well as adding steel fi bers on the compressive strength, modulus of elasticity and indirect tensile strength.
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Abstract

Nano technology is an emerging field of interest for civil engineering application. Among the nano materials presently used in concrete, nano-silica possess more pozzolanic nature. It has the capability to react with the free lime during the cement hydration and forms additional C-S-H gel giving strength, impermeability and durability to concrete. Present paper investigates the effects of addition of nano silica in normal strength concrete. Three types of nano-silica in the form of nano suspension having different amount of silica content have been investigated. Mix design has been carried out by using particle packing method. X-Ray diffraction (XRD) analysis has been carried out to find the chemical composition of control concrete and nano modified concrete. Further, experimental investigations have been carried out to characterize the mechanical behaviour in compression, tension and flexure. It has been observed that the addition of nano-silica in normal strength concrete increased the compressive strength and decreased the spilt tensile strength and flexural strength. Also, Rapid chloride permeability test (RCPT) has been conducted to know the chloride permeability of control concrete, nano modified concrete, and nano coated concrete. It has been observed that the chloride permeability is less for nano coated concrete.
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